Process for cutting helical gear-wheels.



W.P; ZIMMERMANN. PROCESS FOR. CUTTING HELIOAL GEAR WHEELS APPLICATION rum) NOV. 1, 1911.

2 SH ETS-5111331 1.

N \Q WITNEJSEES mil/E TER Patented Aug 27,1912.

W. F. ZIMMERMANN. PROCESS FOR CUTTING HELIOAL GEAR WHEELS.

APPLICATION FILED NOV. 1, 1911.

Patented Aug. 27, 1912.

2 SHEETS-SHEET 2.

INl /CNTUF? WILLIAM F. ZIMIVIERMANN, F NEWARK, NEW JERSEY, ASSIGNOR T0 GOULD & EBER- HARDT, OF NEWARK, NEW JERSEY, .Z-l. CORPORATION OF NEW JERSEY.

rnoonss non CUTTING HELICAL GEAR-WHEELS.

Specification of Letters Patent.

Original application filed October 24, 1907, Serial No. 399,033. Divided and this application filed November 1,1911. Serial no. 657,970.

i To all 'whomt may concern Be it known that 1, WILL'IAM F. ZIMMER- .MANN, acitizen of the United States, and a resident-of Newark, in the county of Essex and State of New Jersey, have invented oer tain'new and useful Improvements in Proc- 4 ess'es for Cutting Helical Gear-VVheels, and

do hereby declare the following specification, taken in connection with the drawings forming part of the same, to be a full, clear, concise, and exact description of the pr1n= ciple ofthe invention and the best'mode con templated to apply said principle, so as' to distinguish it from other inventions and to enableany personskilled in the art to which itappertains or with which it is most nearly connected to make, construct, and use the same.

.The invention relates primarilyto a,

method of generating teeth in helical gear wheels without imparting a difi'erential motion toeithe'r'the blank to be cut or to the! cutter therefor, andmore particularly to a process employing a helical or hob cutter.

This invention is applicable to the apparatus shown and described in a co-pendin application of the applicant, filed October 24th, 1907, Serial No. 399,033, of which case this invention is'a division.

The object of this invention is to provide a process of cutting helical gear wheels with a helical cutter by imparting a single resultant motion to said cutter and blank spindle in contradistinction to a differential motion, and of feeding said cutter parallel to the axis of, and relative to the rotations of said blank spindle, to produce helical teeth having their directrix coinciding with the axis of said blank spindle. The rotational and feeding motions of the cutter and the rotational motion of the blank are in accordance with a' mathematical formula from which on the aforesaid feeding motion being relative to the rotations of the blank'spindle.

The annexed drawings and description "thereof setforth in detail, certain mechanism embodying means constituting, however, but one of the various mechanical forms in which the tion may be used.

The novelty of the invention. will be readprinciple of the invenily understood from the drawings, which show a construction for practising the invention in its preferred form, and from the following description thereof, and is more particularly pointed out and distinctly claimed in the claims annexed to said de scription.

In the drawings Figure 1 is a side view. of the apparatus embodying thefeatures necessary to practise this invention. Fig. Q'is a section through a constant driving train taken at X X of Fig. 1. Fig. 3 is a partial rear elevation partly in section to illustrate the driving mechanism.

In order to fully understand the invention," the formula for determining the relative ratios will be deduced after the follow.- ing notation:

P znormal circular pitch of helical gear to be cut or the shortest distance between any two consecutive teeth and is measured on the normal to the helices and determines the'size of the cutter to be used.

P norm'al diamet-ral pitch of the helical gear and cutter.

P=circular pitch and is measured at right angles to the axis of the gear.

P linear pitch measured parallel to the axis of the gear. N number of teeth in the gear. Dzpitch diameter of the gear. D=outside diameter of the gear.

a addendum. v X=angle of the helices with the axis of the gear.

L=lead of the helices or the advance in one turr,

The following formulae are ordinarily used to determine the various parts of a helical gear when the usual known quantities are given, to wit: P, N and X:

Patented. Aug. 2?, 1912.

cutter is advanced across the face of'theblank in whatresults in a helical path .upon the peripheral face of the blank, passing around, the axis of the blank, such path being due in other machines to differential gears inserted in'the cutter drive or indexing mechanism. This invention produces such a helical path by adding or subtracting a small increment to or from the rotary speed of the blank or'cutter, according to the style of gear to be cut, such increment depending on the relation of the forward motion of the helical cutter to the rotation of the blank spin,dle.- v

To index in a machine, as will be described hereinafter, the formula for the number of teeth would be where K represents a constant depending upon the relative ratios of rotation of the work spindle to that of the helical cutter, and N- represents the number of teeth to be cut. The leadL o the helices as shown above equals sin. tan. X P sin. X

is in which K isa constant depending upon the relative rotational ratios of the work spindle and the helical cutter; N

' V KK sin. X

. its axis, and

equals the number ofteeth to be cut. Letting NPNC sin. X

equal the formula for the lead in which P equals the normal circular pitch of the spiral gear and X the angle of the gears with K tional ratio of the feed train of gearing with the work spindle, in which V is a variable depending upon the ratio of the feed change gears and Kf the relative ratio of the constant feedgearing' with the work spindle. Then since the feed is controlled from the revolutions of thework spindle, we must subtract or add V -NP K from sin. X

represents the relative rot-awhich equals K we have.

KNP FVsin.-X ll KN P FNVsinX K sin. X' K K sin. X which eliminatesthe tooth facton' Then-dividing the feed ratio formula X b KN P N'V sin. X K KK "sin. x which is v KV sin. X

"ITXKWTX iW X) which represents the amount to-beadded or subtracted from the index formula N tain the proper helix of the spiral or chevron gear to be cut.

The above increment is added when using K KV sin.X

a right-hand cutter to cut a right-hand gear or a left-hand cutter to cut a left-hand gear. It is subtracted when using a right-hand cutter to cut a left-hand gear, and when cutting a right-hand gear with a left-hand cutter. Thus the formula becomes:

formula which is composed of the number of revolutions the blankspi'ndle made for indexing, subtracted from the entiie revolutions made by the said blank spindle, the result will equal F 1 which is the extra revolution for the helix, the signs depending upon-the above formula. This can be shown in' the following way: Let

equal the total number of revolutions of the blank spindle and KKP RV sin. X

'tuting in the formula for K a constant value V 60, and K a constant value 16, the formula becomes:

Taking a gear having 40T,5/8P,V=%

and substituting the known values, we have: eeoxs s 1200 16 40 5/'z (1/1 X1/2) 799 the proof formula, we obtain 1200/799X1/1X l/2 the assumption being that the gear was right-hand, using a right-hand'cutter, or

left-hand using a left-hand cutter, and that the cutter was single threaded, if the same had a multiple number of threads proper reduction inthe factor N.

Proceeding now with the detailed description ofthe mechanism to practise the invention, the main frame 1 is provided with a stanchion 2 at one end thereof, preferably cast integral therewith. A work slide 3 is adjustably mounted upon the horizontal portion of themain frame 1', and is provided with a revoluble work spindle 4 there-.

1n, in which the work arbor 5 issecured, whereby the gear blank 6 may be centered and secured to the spindle 4 in the usual .way. A worm or index wheel 7 is secured to the lower end of the Work spindle 4-and rotated by the worm 8 in engagement therewith. The index worm 8 is mounted in the bearings 9 of the Work slide 3, and is provided with a, gear 10 secured toone end thereof to engage with a gear 11, which is slidably keyed to-the index shaft 12. The

index shaft 12 extends along the side of the main frame and is mounted in bearings at either end thereof and connected to the index driving shaft 13 by means of a compound train of change .wheels which are arranged in accordance with the formula hereinbefore described. The change gear 14 secured to the index shaft 12 meshes with a second change gear 15 rotatably mounted upon the stud 16 carried by the arm 17. A third change gear 18, also rotatably mounted on said stud 16 is arranged to rotate in unison with said second change gear 15 and meshes with the change gear 19 secured to and rotatable with the index'driving shaft 13. The stud 16 is slidably arranged in the arm 17 to accommodate various diameter change gears and is secured thereto by the bolt 20. Thearm .17 carrying the stud 16, is pivot-ally mounted upon the index shaft 12, and is secured in the various positions to the index shaft bearing 21 by the bolts 22; The index shaft 12 has also secured th reto and rotatable therewith, a feed driving gear 23 which meshes with one of the two tumbler gears 24 which are rotatably mounted in the tumbler lever 25. A bolt 26 is provided to secure said tuinbler gears 24 in such position that either one of them may be engaged with the feed driven gear 27 which is secured to the feed drive shaft 28. [The change gear 29 is secured to the other end of said feed drive shaft 28 and engages with the change gear 30 to drive the feed of 'the helical cutter as hereinafter described.

.The index drive shaft 13 which imparts motion directly to the gear blank 6 receives its motion fromthe main shaft 31, through the worm wheel 32 secured to said index drive shaft and rotated by the worm 33 secured to and rotatable with said main shaft- 31. The ratio of the worm wheel 32- and the worm 33 must be equal to or a factor of the ratio between the main drive shaft 31 and the helical cutter, preferably the ormer, so that for each rotation of the cutter, the index drive shaft will make a complete rotation or a multiple thereof.

The main drive shaft 31 is rotated by the cone pulley 34 mounted on a hub 35 of the main frame 1, and is connected to said drive shaft v31 by a flange collar 36 which is carried by the main shaft and cone. A helical cutter 37 is secured in anysuitable manner to the cutter shaft 38, mounted to rotate in the swivel carriage 39. The cutter carriage 40 on which the swivel carriage 39. is mounted is vertically movable on the stanchion 2, parallel to the axis of. the gear blank. The swivel carriage is secured to the cutter carriage in any angular position in relation to the gear blank by means .of bolts 41, the heads of which are in a circular T slot 42 arranged in the cutter carriage.

The cutter shaft has secured theretoand rotatable therewith a drive gear 43 meshing gears 47 and 46 is insured in any angular position of the cutter. A bevel gear 49 is secured to the other end of the center shaft 48 and meshes with-the bevel gear 50, which is rotatably mounted in the-cutter carriage and is'slidably keyed to rotate with the vertical cutter drive shaft 51.

The cutter drive shaft 51 is mounted in bearings provided in the stanchion 2. A

bevelgear 52 is secured to the lower end of said cutter drive shaft 51 and is arranged to be engaged by either of the reversing bevel gears 53 or 54, which are slidably keyed to the main drive shaft 31 and carried 'by the yoke or bearing 55. The bevel .gears 53'and 54 are for reversing the direction of rotation of the helical cutter, either one of which may be engagedwiththe vertical shaft bevel gear 52 by the handle 56 which operates the yoke 55. The yoke =55 can be secured to the frame in any position by the'bolt 58. The feed of the cutter parallel to the axis of the. gear blank is obtained from the index shaft 12 through the tumbler gears hereinbefore described, and

the changegears 29 and 30. .From this connection it isobvious that the feeding motion of the cutter is dependent on and relative to the rotations of the blank spindle. A change gear 30 is secured to the feed worm shaft 59, having preferably integral therewith, a. feed worm 60 which engages with the. feed worm wheel 61. A feed screw 62 is mounted in bearings of the main frame and engages a threaded portion 63 of the cutter carriage and is rotated by the feed worm wheel 61, which is secured thereto.

From 'the construction as described it will be seen that the connections between the cutter and blank spindle are such that a continuous and 'unvarying motion can be imparted to said cutter and blank spindle.

And that in practising this inventionit is essential that said cutter and blank spin dle are rotated at certain relative speeds and are fed in respect to each other parallel with the axis of the blank spindle in a cer-.

tain determined ratio, relative to the'rotations of the blank spindle. It is immaterial whether thesource of power is located as shown in the drawings, or whether it is applied at some other point in the mechanism, so long as'the continuous connection between the cutter and blank spindle is maintained. a

The procedure to arrange the apparatus to practise the method of cutting helical gears as herein described, is as follows: The gear blank is mounted on, and secured to the work spindle; the cutter secured to the cutter spindle and the swivel carriage adjusted to the proper anglewith-relation termined are then placed in their proper positions and the machine is ready to operate and will complete the. helical gear by one passage of the cutter across the face of the gear blank.

Having described my method of cutting helical gear wheels with a helical'cutter, I claim as new and desireto secure by Letters Patent: 7

1. A method of cutting helical gear Wheels, consisting of rotating a gear' blank and helical cutter with relative speeds, through a single continuous and unvarying motion from a driver to said gear blank and cutter, respectively, said relative'rotations being determined by the ratio of the number of teeth to be cut to the number of threadsin the cutter, plus or minus an increment dependent upon the amount of feed desired for each rotation of the. gear. blank, and imparting a feedlng motion substantially parallel to the axis of, and relative to the rotations of, the gear blank, to

produce helical teeth on said blank that have a directrix coinciding with' theaxis of the gear blank.

2. A method of cutting helical gear wheels, consisting of rotating a gear blank and helical cutter with relative speeds, through a single continuous and unvarying motion from a driver to said gear blank and cutter, respectively, said relative rotations being determined by the ratio of the linear, ,3 *5- pitch of said gear to the lead of said gear plus or minus the amount of feed desire-dv for each rotation of the gear blank, and imparting a feeding motion substantially parallelto the axis, and relative to the rotations of said gear blank, to produce helical teeth on said gear that have a directrlx coinciding with the axis of said blank.

WILLIAM F. ZIMMERMANN. Witnesses: j B. E. BARNES, I j H. W. JAooBsoN. 

